Power semiconductor modules comprise a semiconductor package and at least two semiconductor chips mounted on one or more substrates in the package. The power semiconductor chips usually comprise power electronic circuits such as rectifier bridges, DC-links, Insulated Gate Bipolar Transistor (IGBT) inverters, drivers, control units, sensing units, half bridge inverters, AC-DC converter, DC-AC converters, DC-DC converters, bidirectional high bridge switches, and more.
Modern power semiconductor modules commonly use leadframes for external contact. The leadframe is electrically contacted to the substrate whereon each of the internal contacts of the semiconductor chips are connected to the leads of the leadframe. For an extended circuit area on the substrate the lead contacts are electrically connected exclusively to the sides of the substrate. A technique for the enclosure of semiconductor modules is the Insert-Mold-Technique (IMT) wherein the semiconductor chips mounted on one or more substrates are molded in a housing of a synthetic material. In case of the manufacture of an IMT-module housing, the leads of the leadframe extending away from the substrate are connected by a circumferential leadframe bar acting as a sealing interface between an upper and lower die during the IMT-manufacturing process.
For electrical isolation and mechanical protection, the power semiconductor modules are encapsulated. After completion of the module housing, the power semiconductor module is mounted on a cooling element for dissipating excess heat of the semiconductor chips generated during operation. An effective thermal contact is achieved by closely mounting a large area of the power semiconductor module, e.g. the bottom side of the module, onto a surface of the cooling element acting as a heat sink.
To reduce the costs of the synthetic module housing material the body of the power semiconductor module usually has a flat shape. This shape leads to small heights of the power semiconductor modules resulting in small distances between the top side of the power semiconductor module and the cooling element where the module is mounted on.
The afore mentioned leadframe contacts protrude the module housing on the sides of the power semiconductor module body. Due to the flat shape of the power semiconductor module, the small distance of the electrical contacts to the cooling element, often just a few millimeters, result in small creepage distances and air gaps between the electrical contacts of the power semiconductor module and the cooling element. The use of conventional power semiconductor modules is thus limited to reverse voltages of approximately 600 V. For operation at higher reverse voltages, particularly in the widely used reverse voltage class of 1200 V, additional measures and efforts are required for a reliable operation of these power semiconductor modules. There is a general need to provide power semiconductor modules for operation at reverse voltages beyond 600 V without the need of subsequent time and effort consuming treatments of the modules.